1. Field of the Invention
The present invention relates to a lip type seal corresponding to one kind of a sealing apparatus. The lip type seal in accordance with the present invention is used, for example, as a water pump seal for a vehicle such as a motor vehicle or the like, or is used as the other general purpose water pump seal.
2. Description of the Conventional Art
Conventionally, as shown in FIG. 3, there has been known a lip type seal 74 which is installed to an inner periphery of a shaft hole 72 of a housing 71 and slidably comes into close contact with a peripheral surface of a shaft 73 inserted to the shaft hole 72, and the lip type seal 74 has a first seal lip 75 which is arranged at a sealed fluid side A and is made of a rubber-like elastic material, and a second seal lip 76 which is arranged at an atmospheric air side B and is made of a resin (refer to patent Japanese Unexamined Patent Publication No. 10-318377).
Since the conventional lip type seal 74 mentioned above has a plurality of seal lips 75 and 76, each of which performs a seal operation, an excellent seal effect can be achieved, however, has a disadvantage in the following point.
On the basis of a request on recycle in respect to an environmental problem in recent years, disposal of each of constructing parts of the lip type seal is required to be done after being sorted by material. However, in the conventional lip type seal 74 mentioned above, the first seal lip 75 made of the rubber-like elastic material is bonded by vulcanization to a reinforcing ring 77 made of a metal, and both the parts 75 and 77 are formed as an integral product which has been vulcanized and molded. Accordingly, it is impossible to easily separate and sort both the parts 75 and 77 at a time of disposal, and it is therefore impossible to comply with the request on the recycle.
Accordingly, the applicant of the present invention has previously proposed a lip type seal 81 having a first lip seal member 82 provided with a first seal lip 83 arranged at a sealed fluid side A and made of a rubber-like elastic material, a second lip seal member 84 provided with a second seal lip 85 arranged at an atmospheric air side B and made of a resin, and two retaining rings 86 and 87 provided for pinching both the lip seal members 82 and 84 from both sides in an axial direction and made of a metal, and having a structure in which these four parts are assembled in a non-bond manner, as shown in FIG. 4 (refer to WO2004/076894A1). In accordance with this prior art, since each of the parts is not bonded, it is possible to easily separate and sort each of the parts. Accordingly, it is possible to comply with the request on the recycle mentioned above. However, as for the prior art, there is room for improvement in the following points.
(1) Assembly Retaining Characteristic Between Constructing Parts
In the lip type seal 81 mentioned above, two retaining rings 86 and 87 are structured such that they have annular flat surface portions 86a and 87a respectively for pinching both the lip seal members 82 and 84 from both sides in an axial direction and tubular portions 86b and 87b are integrally formed on the flat surface portions 86a and 87a. The tubular portion 86b of the retaining ring 86 at the sealed fluid side A, is fitted to an inner peripheral side of a cylinder portion 82a of the first lip seal member 82 and the tubular portion 87b of is the retaining ring 87 at the atmospheric air side B pressure-inserted and fixed to an insertion hole 82b provided in the cylinder portion 82a of the first lip seal member 82. Accordingly, each of the parts is retained in an assembled state on the basis of setting of a fitting margin and a pressure-inserting margin for the fitting and pressure-insertion. However, an engagement structure for preventing separation between the parts in an axial direction, in the case that each of the parts is exposed to force in the axial direction, is not particularly provided between each of the parts. Therefore, when the retaining ring 86 at the sealed fluid side A is pulled in an axial direction (a direction of an arrow C) in order to detach the lip type seal 81 in a state of being installed to an inner periphery of the shaft hole 72 of the housing 71, there is a case that only this retaining ring 86 is pulled out and the other parts remain in an installed state (or there may be a case that only the retaining ring 86 and the first lip seal member 82 are pulled out, and the second lip seal member 84 and the retaining ring 87 at the atmospheric air side B remain). This is because of nothing but the assembling retaining force between the parts depending only upon friction force.
(2) Installing Workability
Further, in the lip type seal 81 mentioned above, two retaining rings 86 and 87 do not particularly have any structure for defining an interval between them in an axial direction. Further, the first lip seal member 82 pinched between both the rings and made of a rubber-like elastic material can achieve a sufficient seal operation only by being used in a state of being compressed in the axial direction. In other words, there is a risk that a leakage of a sealed fluid may occur from the portion between it and the first lip seal member 82 or the second lip seal member 84 made of a resin or the retaining ring 87 at the atmospheric air side B. Accordingly, at a time of installing the lip type seal 81 mentioned above, the lip type seal 81 is installed by using a snap ring 89 while bringing the lip type seal 81 into contact with a step portion 88 provided at an inner periphery of the shaft hole 72 of the housing 71 and applying a compression load in the axial direction, whereby the lip type seal 81 is installed in a state that the whole thereof is compressed in the axial direction between the step portion 88 and the snap ring 89. However, there is such a disadvantage that a work of installing by using the snap ring 89 while applying the compression load in the axial direction as mentioned above is extremely complicated.
Further, since the cylinder portion 82a of the first lip seal member 82 is provided with the annular insertion hole 82b which is open to the atmospheric air side B, a portion at an outer peripheral side from the insertion hole 82b in the cylinder portion 82a is formed in such a shape that an atmospheric air side end portion 82c thereof terminates so as to keep a cylindrical shape. Accordingly, since the atmospheric air side end portion 82c rubs the inner peripheral surface of the shaft hole 72 at a time of inserting the first lip seal member 82 into the inner periphery of the shaft hold 72 of the housing 71, there is a case that an evagination occurs in the atmospheric air side end portion 82c. 
Further, in a bonded type lip seal in which the seal lip 75 made of a rubber-like elastic material is bonded by vulcanization to the reinforcing ring 77 made of a metal as shown in FIG. 3, there is pointed out a problem of foaming resistance. In particular, according to a tendency for a higher speed and a higher temperature of an engine in recent years, cooling water of a water pump for cooling the engine tends to have a high temperature and a high pressure, and a seal portion ambient atmosphere becomes severe. In the bonded type lip seal under the use condition mentioned above, since the seal lip 75 made of a rubber-like elastic material and the reinforcing ring 77 made of a metal are bonded, there is a case that a foaming phenomenon occurs in the seal lip 75 in the case of being used under a high load condition, thereby causing reduction of a sealing performance.